Concrete Masonry Hollow Block

ABSTRACT

A building block having a body with three sets of opposing outer sides defining a generally rectangular outer shape, the body having at least one passageway having an upper open end at a top of the block and an open lower end at a bottom of the block. An inner part of the block is comprises of a first material, and a second different material surrounds the inner part providing a substantially continuous outer surface of said second material. At least one side of one of the sets of opposing sides has at least one protrusion extending outwardly therefrom, and at least one cavity is provided in the opposed side in a position and of a size to receive and effect an alignment of a further block having the same shape and size of this first defined block, by receiving the at least one protrusion into the cavity or cavities.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/299,345, filed Nov. 3, 2008, which is a §371 National Phase ofPCT/AU2007/000622, filed May 10, 2007, the entirety of which areincorporated herein by reference.

TECHNICAL FIELD

This invention relates to a concrete masonry unit such as a buildingblock, a construction with concrete masonry units, and a method ofconstruction using these concrete masonry units.

BACKGROUND ART

It is known to use concrete hollow blocks for building. These aretraditionally made from a very dry no-slump concrete being a cement andaggregate mixture. This mixture is compressed and/or vibrated while in amould to an extent to be self-supporting, and then subsequently quicklyremoved from the mould and handled for curing and other treatment awayfrom the mould.

Such traditional blocks also are traditionally used in construction byusing a wet mortar bed on which each block is supported. Each block isadjusted in position by a skilled tradesman to be appropriately aligned,then the mortar is left to cure. Such cure can take such time that itmay limit the number of blocks that can be located one above the otherin a single session.

Costs associated with the construction then are driven by a need forskilled tradesman to prepare each mortar bed, apply end mortar where theblock none the less is very heavy in most cases, and then adjust a finallocation for alignment of the block with other of the blocks alreadypositioned.

A further challenge with traditional masonry concrete blocks is theirappearance.

An object of this invention is to reduce at least to some extent one ormore of the above difficulties.

Other objects and advantages of the present invention will becomeapparent from the following description, taken in connection with theaccompanying drawings, wherein, by way of illustration and example, anembodiment of the present invention is disclosed.

DISCLOSURE OF THE INVENTION

In one form of this invention there is proposed a building block havinga body with three sets of opposing outer sides defining thereby agenerally rectangular outer shape, the body having at least onepassageway having an upper open end at a top of the block and an openlower end at a bottom of the block, an inner part of the block being ofa first material and a second different material from said firstmaterial surrounding the inner part providing thereby an at leastsubstantially continuous outer surface of said second material, and aone side of a one of the sets of opposing sides having at least oneprotrusion extending outwardly from a planar surface of the side, and atleast one cavity in the further opposed side of the same set of opposedsides in a position and of a size to receive and effect an alignment ofa further block having the same shape and size of this first definedblock, by receiving a or the protrusions into the cavity or cavities.

Preferably, the second material is denser than the first material.

Preferably, the second material is a cementitious material.

Preferably, the second material is made from a mix comprising at leastin the main, cement, sand and water.

Preferably, the first material is a mixture of expanded plasticparticles and a cementitious binder.

Preferably, the first material is a mixture including at least in themain, cement, sand, water and expanded polystyrene beads.

Preferably, the first material includes an additive to ensure that theexpanded polystyrene particles or beads are compatible with the wetmixture, and be mixable therewith.

Preferably, the additive is added to the water prior to the drycomponents being added to the same.

Preferably, the outwardly extending protrusion extends from an upperface of the block, and the cavity is formed in the bottom or underneathface of the block, and wherein in use, the cavity is adapted to acceptan outwardly extending protrusion of a further block for the purpose ofjoining and causing to be aligned the two building blocks.

Preferably, one or more slots divide the outwardly extending protrusion,so that a further block can register and nest therewith in either anoverlapping or fully coincident registering position.

Preferably, the protrusions are substantially rounded.

Preferably, in the alternative, the protrusions are of a substantiallyrectilinear shape

Preferably, the protrusions are orthogonally symmetrical with respect tothe block,

Preferably, there are two passageways extending between the top andbottom of the block, these being divided by a wall extending betweenside walls of the block so as to be integral therewith.

Preferably, the cavity is defined by a skirt extending around a lowerperimeter of the block so as to be integral therewith.

In a further form, the invention may be said to reside in a buildingblock of wet cast cement having, as integral portions, two oppositelypositioned side walls and two oppositely positioned end walls whichtogether define at least one inner passageway extending fully throughthe block from a bottom to a top thereof, an outer, uppermost perimeterof the block being substantially within a single plane, and a portion ofthe respective walls behind the outer uppermost perimeter being higherthan the outer uppermost perimeter, an outer, lowermost perimeter of therespective walls together all being within a single plane, and a portionof the respective walls behind the outer lowermost perimeter beinghigher than the outer perimeter, and wherein said latter portion ispositioned and shaped so that it provides a receiving shape, where anidentical block, if resting on the first block so as to have alignedouter most is side faces, would have its outer lowermost perimetersubstantially coincide with the outer uppermost perimeter of the firstblock.

In a further form, the invention may be said to reside in a buildingblock of wet cast cement having, as integral portions, two oppositelypositioned side walls and two oppositely positioned end walls whichtogether define at least one inner passageway extending fully throughthe block from a bottom to a top of the block, an outer uppermostperimeter of the respective walls together all being within a singleplane, and a portion of the respective walls behind the upper outeruppermost perimeter being higher than the outer perimeter, an outerlowermost perimeter of the respective walls together all being within asingle plane, and a portion of the respective walls behind the outerlowermost perimeter being higher than the outer perimeter, and whereinsaid latter portion is positioned and shaped so that it provides areceiving shape where an identical block, if resting on the first saidblock so as to have aligned outermost side faces, would have its outerlowermost perimeter substantial coincide with the outer uppermostperimeter of the first said block.

In a further form, the invention may be said to reside in a buildingblock which is of substantively rectangular external shape with twooppositely positioned outer sides, two oppositely positioned outer endsand a top and bottom, a hollow passageway extending fully through theblock from the top of the block through to the bottom of the block, aplurality of protrusions each extending above a plane defined by a topof the block, each protrusion being located so as to have an inner sideadjacent or adjoining to extend along a portion of a perimeter at a topof the hollow passageway, and one or more receiving cavities extendinginto the planar surface of the bottom of the block, the or no eachcavity corresponding in shape and location so as to receive a one ormore protrusions extending into the bottom surface, and where therespective protrusions and cavity or cavities are in respectivelymutually corresponding positions.

In a further form, the invention may be said to reside in a constructionin which a first building block as described above, is positioned on asecond, substantially identical block, the first block having upwardlydirected protrusions engaging corresponding cavities within theunderneath face of the second block.

Preferably, the respective blocks are held together by a buildingadhesive.

In a further form, the invention may be said to reside in an assembly ofat least two blocks, each of which is as described above, where thedimensions and shape of a first of the blocks are substantiallyidentical to the dimensions and shape of a second of the blocks, wherethe first of the blocks is positioned above and aligned to have a frontand rear face of each define a common plane and where the first blockwith its bottom face is resting on, directly aligned and adhering by athin adhesive interface extending at least substantially between the twomating faces of the respective blocks.

The term “wet cast concrete” is used to distinguish this concrete asrequiring somewhat longer in a mould before it can be released ascompared to blocks using very dry no-slump concrete, which is compressedand/or vibrated into a compact mass that can be removed from a mouldvery promptly after such a process, and can be cured out of the mould.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of this invention it will now be describedwith reference to preferred embodiments which shall be described withthe assistance of drawings wherein:

FIG. 1 is a perspective view of a first embodiment from above a block;

FIG. 2 is a perspective view of the first embodiment from below theblock,

FIG. 3 is a perspective from above the block but viewing the block froman opposite side to the first view in FIG. 1;

FIG. 4 is a plan view of the same first embodiment;

FIG. 5 is a side elevation of the first embodiment with a part cut away;

FIG. 6 is an end view with a part cut away of the first embodiment;

FIG. 7 is a perspective view of two blocks according to the firstembodiment positioned in a supporting registration and including anadhesive therebetween;

FIG. 8 is a cross sectional view of the two blocks one upon the otheraccording to a second embodiment;

FIG. 9 is a cross sectional view in an opposite alignment of the twoblocks as in FIG. 8 one upon the other according to the secondembodiment;

FIG. 10 is a perspective view of blocks according to the secondembodiment being joined to illustrate a construction assembly;

FIG. 11 is a cross sectional view of a set of blocks according to thesecond embodiment arranged in an interlocking, joined and adheredarrangement;

FIG. 12 is a Cross sectional view of a block according to a thirdembodiment;

FIG. 13 is a perspective view from above of a fourth embodiment;

FIG. 14 is a perspective view of the same fourth embodiment when viewedfrom below;

FIG. 15 is a cross sectional view of the blocks of the fourth embodimentin an assembled arrangement;

FIG. 16 is a perspective view of a fifth embodiment;

FIG. 17 is a perspective view of the same fifth embodiment when viewedfrom below;

FIG. 18 is a cross sectional view of the blocks of the fifth embodiment;and

FIGS. 19 and 20 are perspective views of a sixth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Now referring to the drawings in detail, FIGS. 1 through 7 refer to afirst embodiment where there is a block 1 formed of a wet cast cementand having as integral portions, two oppositely positioned (i.e.opposing) side walls 2 and 3, and two oppositely positioned (i.e.opposing) end walls 4 and 5 where each of these walls 9, 3, 4 and 5 areintegrally molded.

The alignment of these respective walls 2, 3, 4 and 5 is such that thereis defined therebetween, in this particular case a hollow passageway 6in the one case, and 7 in the other.

An advantage of these passageways 6 and 7 is that they render the block1 lighter than a block of equivalent size and composition wouldotherwise be. Moreover, these cavities provide an insulating effect,which can prove to be useful both from an energy saving perspective, butalso in terms of fire resistance.

There is an intermediate joining wall 8 which extends transversely fromwall 2 to wall 3 and is integrally molded therewith as well.

There is provided in this block an upper outermost perimeter 9 and thissubstantially defines a plan at 10. With reference to this plan 10 thereis a portion of the block exemplified by the respective portions such asat 11, 12, 13 and 14 as examples, which provide a higher part (i.e. forma projection) which is positioned so as to leave a surrounding borderarea 15 which is a part of the defined plan 10 and the higher portionsare set back and, in this embodiment.

The higher portions (projections) 11 through 14 typically are raised butare separated by portions which leave an area consistent with the planas in 10 and the purpose of these “slots” shown for instance at 17 and18 is to allow for a similar block to register and nest appropriatelywhether in an overlapping or fully coincident registering position.

Rounding these higher portions 11 through 14 as shown in FIGS. 1 through12 is considered preferable, because these rounded shapes are morerobust than higher portions having sharp edges, which have a greaterpropensity to chip and break with use.

An advantage of the raised portions is that they implicitly provide ashape which is offset from an outer edge, but is raised therefrom andthis implicitly acts as “a flashing” to retard access of moisturetherepast.

This effect is to some extent prejudiced by the slots 17 and 18, but thearea provided by the slots is relatively small as compared to theoverall length of the upper portions 11 through 14 so that the prejudiceeffect is relatively small.

Now looking at the underneath side as perhaps shown in FIG. 2 but it isalso shown in other of the Figures, there is a lowermost outermostperimeter 20 which defines a lowermost plan 21.

In this case, this then provides what might be termed a skirt, whichfully surrounds the lowermost portion of the block 1 and inset from thisplan 1 is a raised portion 22 the location of which and the height ofwhich relative to the plan 21 is chosen so as to be coincident withinseveral millimetres of the respective plan 10 and the raised portionstypically 11 through 14.

In this particular case, the dimensions have been chosen so that thearea provided by the lowermost plan 21, and to some extent the plan 10,are approximately the same as the area provided by the plan 22 and theplan 16.

When a first block is located on a second block, it can therefore beexpected that there will be a sharing approximately equally of the loadon face to face contacts and, except to the extent that there is anadhesive in the construction technique in this case, the faces willengage closely one with the other and provide this support.

Further however, an advantage of having an approximately similar widthis that the upper portions during handling are relatively sturdy, andthe skirt portion depending from a bottom of the block is alsorelatively sturdy and will be more resistant to being broken duringconventional or even rough handling in a construction site.

It is noted that the underneath side of the block 1 does not attempt toprovide separate portions which will fit within respective slots such as17 or 18.

The construction of this block 1 is a wet cast construction techniquewhich means that it will depend upon curing of the cement at least tosome extent before it can be self supporting and therefore able to beextracted from a die for its forming.

This is distinguished then from a conventional compressive masonry castblock system, where very dry or in terms of the trade no or negligibleslump concrete is used and use of vibration and or pressure enablesrapid extraction from a die, so that it is only subsequent to extractionthat any substantive curing of the cement would be expected and this canbe achieved in appropriate ways for instance by steam curing or by anyother conventional technique.

We are using in this particular embodiment and at least in relation to asubstantive part of the application and the invention, portions of theblock which are of different characteristics.

An inner characteristic is of a concrete, which is formed with Portlandcement, sand and polystyrene beads.

This has been found to be an effective material, which can provideadequate structural strength for the inner part of a block of this type,and an outer part of the block is provided by a separate facingmaterial, which is not including material such as expanded plastics.

It is known to treat polystyrene beads with an appropriate coating sothat they will be mixable with wet cement especially Portland cement andit is proposed in this case that such a mixture should be used. Thebeads may be treated prior to their addition to the mixture, or indeedthe protective additive may be mixed in with the dry mix, or indeed withthe water before the dry mix is added.

The advantage of using polystyrene beads is that there can be provided alightweight concrete which can have an adequate compression strength butcan also provide a block size which makes for economic handling andstorage and indeed manufacture and by providing a facing material whichcan be of a conventional cement sand mix applied and integrated with theinner core material of the foam: sand or other aggregate, and cement,means that overall, the external face can be chosen to be decorative, orimpermeable to moisture, or otherwise appropriate for otherapplications, while the inner body provides this adequate supportstrength and at the same time the bulk for the purpose needed.

A typical mixture for the inner core material can be as follows (perblock):

Polystyrene: 6.5 L to 7 L

Cement: 4 kg to 5 kg

Sand: 5 kg to 5.5 kg

Water: 1.8 L to 2.1 L

Supa Plastecizer 14 mL to 20 mL

Calcium chloride: 50 mL to 65 mL

Air entraining agent: 14 mL to 20 mL,

Further to this, a typical outer layer mixture is (per block):

Sand 0.55 kg to 0.58 kg

Cement: 0.3 kg to 0.4 kg

Polystyrene beads that have been appropriately treated can be purchasedfrom conventional suppliers.

Further to this, a typical outer layer mixture is (per block):

Polystyrene beads that have been appropriately treated can be purchasedfrom conventional suppliers.

There are features with this block 1 that assist in manufacture and use.

A first of these is that the inner passageway is defined by sides whichare aligned to be tapering so that the sides for instance 21 and 22which are oppositely positioned one with respect to the other and thesides 23 and 24 which are also oppositely positioned to each other aretapered so that they have a wider and broader upper mouth than the mouthat the lower end 25.

This allows for easier core extraction during manufacture namelysubsequent to the block having been cast and ready to be extracted fromthe die.

This has the advantage of also assisting in die extraction but it alsoassists when one block is placed upon another in that this tapered shapeacts as a lead in when the bottom of the block 1 is being brought overcorrespondingly shaped upwardly projecting portions of a similar blockbeneath it.

The degree of taper can lie within a significant range from as little as1 or 2° up to 45° or more to the vertical.

The lowermost cavity shape is defined also by side walls such as at 28and 29 and these are also then chosen to match the rounded shape of theupwardly projecting portions at 26 and 27.

The block 1 further includes on an outer uppermost edge, an aris 30 andon a lower outermost edge an aris 31.

In FIG. 7, there are two blocks which are now referred to as 32 and 33which replicate the block of the first embodiment and these are nowshown one upon the other in a registered alignment where upwardlyprojecting portions such as 34 nest within correspondingly shapedcavities.

The two blocks have both upper and lower ariss at 35 and 36 and 37 whichfeature provides to some extent decorative as well as functional featurein minimising accidental chipping of the edge which could then bevisually less preferred.

The two blocks in this case 32 and 33 are joined together by a buildingadhesive material; an appropriate material for this purpose is aconventional cementitious adhesive.

In order to join the two bricks or blocks together, a bead of theadhesive material is fed onto the respective meeting surfaces and theextent of this spread is such that when the two meeting surfaces cometogether the adhesive will be caused to spread substantially fullythrough all of the respective surfaces so as to provide not only anadhesion between the respective surfaces and therefore adhering theblocks together, but also providing a sealing but as well against wateringress.

The amount of adhesive needed can be judged in practice and is chosengenerally so that there is approximately a 2 millimetre separation gapbetween the meeting surfaces which is just enough to allow for anadhesive body of material and at the same time the dimensions of therespective mating surfaces are chosen to allow for this smallseparation.

The separation is chosen however so that in practice, once the blocksare positioned, they will be generally centrally aligned and will besufficiently accurately aligned whether one upon the other or whether inoverlapping or corner bonded locations to then need either negligible orno further adjustment in position.

FIG. 8 is a cross sectional view through the assembled blocks as shownin FIG. 7.

FIG. 10 illustrates the same block as in the first embodiment when usedin an overlapping arrangement to provide for a construction.

The blocks in each case in this instance are half overlapping and thereis provided a quarter block 41 to fill the gap created by overlappingthe blocks in this fashion.

The blocks shown here as 40 have the same features as the block in thefirst embodiment and are held together in this case both by buildingadhesive as previously described.

The quarter block in this case 41 is made from a solid masonry concretematerial including in this case polystyrene beads and having an outerface consistent with the outer faces of the other blocks 40 which ismade during a wet cast molding process to not be so embedded withpolystyrene beads or the like.

A cross section of the construction as shown in FIG. 10 is now shown inFIG. 11 an alternative to the cross sectional shape of the upwardlyprojecting portions in the block as shown in relation to the firstembodiment can be altered and alternatives are now shown through theremainder of the embodiments which for instance is shown in FIG. 12where the upwardly projecting portions shown at 45 takes over as amajority of the interface support and there is a much narrower edge at46 providing the defining plan of the upper outermost edge.

Further, the side wall 47 is in case somewhat more extensively sloping.

The blocks otherwise include the polystyrene bead embedded masonrymaterial at 48, an outer facing material formed in a wet cast method butin this case without the embedded polystyrene beads as being shown at 49and the blocks in this case are adhered together by a building adhesivematerial leaving several millimetres separation gap at 50 butnonetheless such that this separation is incidental to the generaldimensions of any construction.

Now referring to FIGS. 13, 14 and 15, these shown a different upwardprojecting portion where this is shown as a triangular cross sectionalshape as typically at 51.

This can then be centrally located along and a corresponding edge cavity53 is in the bottom as shown specifically in FIGS. 14 and 15.

FIGS. 16, 17 and 18 illustrate an alternative shape where the upwardlyprojecting portions as in 55 with reference to an otherwise definingplan 56 is of rectilinear shape in cross section.

This again has a matching cavity shape as shown in FIG. 17 in particularat 57.

Finally there is shown in FIGS. 19 and 20, a further variant of theupwardly projecting interlocking shape as shown at 60 with reference toa defining plan 61 and a corresponding cavity shape 62 within the bottomof the block.

Although the invention has been herein shown and described in what isconceived to be the most practical and preferred embodiment, it isrecognised that departures can be made within the scope of theinvention, which is not to be limited to the details described hereinbut is to be accorded the full scope of the appended claims so as toembrace any and all equivalent devices and apparatus.

1. A building block comprising: a body with three sets of opposing outersides defining thereby a generally rectangular outer shape; the bodyhaving at least one passageway having an upper open end at a top of theblock and an open lower end at a bottom of the block; an inner part ofthe block being of a first material; a facing on at least selected outersurfaces of the block being of a second material different from saidfirst material; at least one side of one of the sets of opposing sideshaving at least one protrusion extending outwardly from a planar surfaceof the side; and at least one cavity in a second opposed side of thesame set of opposed sides in a position and of a size to receive andeffect an alignment of a further block having the same shape and size ofthis first defined block, by receiving said at least one protrusion ofthe first defined block into the at least one cavity of the furtherblock.
 2. The building block as in claim 1, wherein the second materialis denser than the first material.
 3. The building block as in claim 2,wherein the second material is a cementitious material.
 4. The buildingblock as in claim 3, wherein the second material is made from a mixcomprising at least in the main, cement, sand and water.
 5. The buildingblock as in claim 1, wherein the first material is a mixture of expandedplastic particles and a cementitious binder.
 6. The building block as inclaim 5, wherein the first material is a mixture including at least inthe main, cement, sand, water and expanded polystyrene beads.
 7. Thebuilding block as in claim 6, wherein the first material includes anadditive to ensure that the expanded polystyrene particles or beads arecompatible with the wet mixture, and be mixable therewith.
 8. Thebuilding block as in claim 1, wherein the outwardly extending protrusionextends from an upper face of the block, and the cavity is formed in thebottom or underneath face of the block, and wherein in use, the cavityis adapted to accept an outwardly extending protrusion of a furtherblock for the purpose of joining and causing to be aligned the twobuilding blocks.
 9. The building block as in claim 1, wherein one ormore slots divide the outwardly extending protrusion, so that a furtherblock can register and nest therewith in either an overlapping or fullycoincident registering position.
 10. The building block as in claim 9,wherein the protrusions are orthogonally symmetrical with respect to theblock.
 11. The building block as in claim 1, wherein the cavity isdefined by a skirt extending around a lower perimeter of the block so asto be integral therewith.
 12. A building block including two oppositelypositioned side walls and two oppositely positioned end walls whichtogether define at least one inner passageway extending fully throughthe block from a bottom to a top of the block, an outer uppermostperimeter of the respective walls together all being within a singleplane, and a portion of the respective walls behind the upper outeruppermost perimeter being higher than the outer perimeter, an outerlowermost perimeter of the respective walls together all being within asingle plane, and a portion of the respective walls behind the outerlowermost perimeter being higher than the outer perimeter, wherein saidhigher portion of the respective walls is positioned and shaped so thatit provides a receiving shape where an identical block, if resting onthe first said block so as to have aligned outermost side faces, wouldhave its outer lowermost perimeter substantial coincide with the outeruppermost perimeter of the first said block, and where an inner part ofthe block is of a first material and there is a second differentmaterial from said first material providing a facing on at leastselected outer surfaces thereof.
 13. A building block which is ofsubstantively rectangular external shape with two oppositely positionedouter sides, two oppositely positioned outer ends and a top and bottom,a hollow passageway extending fully through the block from the top ofthe block through to the bottom of the block, a plurality of protrusionseach extending above a plane defined by a top of the block, eachprotrusion being located so as to have an inner side adjacent oradjoining to extend along a portion of a perimeter at a top of thehollow passageway, and one or more receiving cavities extending into theplanar surface of the bottom of the block, said one or more cavitiescorresponding in shape and location so as to receive one or more of saidprotrusions extending into the bottom surface, wherein the respectiveprotrusions and cavity or cavities are in respectively mutuallycorresponding positions, and wherein an inner part of the block is of afirst material and there is a second different material from said firstmaterial providing a facing on at least selected outer surfaces thereof.14. A construction comprising at least one a first building blockaccording to claim 1, wherein the first block is positioned on a second,substantially identical block, the first block having upwardly directedprotrusions engaging corresponding cavities within the underneath faceof the second block.
 15. The construction as in claim 14, wherein therespective blocks are held together by a building adhesive.
 16. Anassembly comprising at least two blocks according to claim 1, whereinthe dimensions and shape of a first of the blocks are substantiallyidentical to the dimensions and shape of a second of the blocks, whereinthe first of the blocks is positioned above and aligned to have a frontand rear face of each define a common plane and wherein the first blockwith its bottom face is resting on, directly aligned and adhering by athin adhesive interface extending at least substantially between the twomating faces of the respective blocks.
 17. A construction comprising atleast one a first building block according to claim 12, wherein thefirst block is positioned on a second, substantially identical block,the first block having upwardly directed protrusions engagingcorresponding cavities within the underneath face of the second block.18. The construction as in claim 17, wherein the respective blocks areheld together by a building adhesive.
 19. An assembly comprising atleast two blocks according to claim 12, wherein the dimensions and shapeof a first of the blocks are substantially identical to the dimensionsand shape of a second of the blocks, wherein the first of the blocks ispositioned above and aligned to have a front and rear face of eachdefine a common plane and wherein the first block with its bottom faceis resting on, directly aligned and adhering by a thin adhesiveinterface extending at least substantially between the two mating facesof the respective blocks.
 20. A construction comprising at least one afirst building block according to claim 13, wherein the first block ispositioned on a second, substantially identical block, the first blockhaving upwardly directed protrusions engaging corresponding cavitieswithin the underneath face of the second block.
 21. The construction asin claim 20, wherein the respective blocks are held together by abuilding adhesive.
 22. An assembly comprising at least two blocksaccording to claim 13, wherein the dimensions and shape of a first ofthe blocks are substantially identical to the dimensions and shape of asecond of the blocks, wherein the first of the blocks is positionedabove and aligned to have a front and rear face of each define a commonplane and wherein the first block with its bottom face is resting on,directly aligned and adhering by a thin adhesive interface extending atleast substantially between the two mating faces of the respectiveblocks.